The fire is burning just one kilometre from the township of Bugaldie and is travelling in a northerly direction away from Timor Road and the Siding Spring Observatory, which was damaged on Sunday night.

Five outer buildings were damaged at the $80 million observatory, while the RFS says another 33 properties were destroyed in the Timor Road area.

It says the number of properties destroyed will likely rise as fire crews work through the area but it is a miracle no lives have been lost.

Overnight 80 fire crews worked to control the blaze and a further 18 aircraft were sent to the area to drop water and fire retardant.

RFS Inspector Brett Lachlan warns residents west of Warrumbungle Park they could also come under threat if crews fail to contain the fire's western flank.

"They have a lot of work to do, to try and take advantage of the overnight cooler conditions to do backburning," he said.

"We have a large number of fire trucks obviously at Bulgaldie, prepared for whatever might eventuate."

Most residents have been evacuated to Baradine and Coonabarabran.

An evacuation centre has been opened at Tattersalls Hotel in Wellington Street, Baradine, for affected residents.